Fibrous insulation products are available in various densities for use in a variety of different environments. One such product is a lightweight glass fiber blanket used to insulated structure which requires a high degree of insulation, such as aircraft hulls. In such an environment it is important that the weight be minimal, so as not to add unnecessarily to the weight of the aircraft, and that the blanket be capable of providing an effective barrier to the high sound levels and cold temperatures encountered during flight.
Typical products utilized for this purpose are comprised of fine glass fibers bonded together in blanket form and having a density of about 0.3 pound per cubic foot (pcf) to 1.5 pcf. Depending on the dimensions of the space required to be insulated, either a single blanket or several stacked blankets are wrapped and secured within a film, as by sewing or heat sealing, and the wrapped insulation is then attached to the aircraft fuselage by pins connected to the skin of the aircraft. While such products perform their insulating function satisfactorily, their relatively low tensile strength offers little resistance to stresses encountered during fabrication and installation. Handling of the individual layers and fabrication of the multi-layered product subject the material to additional stresses which tend to damage the weak fiber glass material.
In addition, because the commercial product usually requires an outer film to allow the insulating blanket to be handled and installed as desired, the effectiveness of the insulation will be reduced in service if condensation of water vapor is trapped within the insulation by the film.
It has been suggested to replace the conventional insulation product discussed above with a lightweight fiber glass insulation blanket having an air-permeable backing sheet adhered to one of the major faces of the blanket, with the other major face and the elongated edges of the blanket being encapsulated within a non-porous film or other material such as the porous backing material itself The backing improves the tensile strength of the insulation product and increases its stiffness. Further, its permeability permits the free passage of air in and out of the blanket. This in turn allows the evaporation of any moisture from installed insulation, such as would be encountered in an aircraft installation, when the insulation is installed with the facing material facing the passenger side of the aircraft.
Such a product could of course be fabricated by the installer of the insulation by separately purchasing the fiber glass blanket, the permeable backing sheet and the non-porous film and attaching the backing and facing materials to the blanket. It would, however, be much preferable to the installer to purchase a fully formed product ready for use directly from the fiber glass producer. This in turn requires the fiber glass producer to be able to rapidly and economically mass produce such an encapsulated product without the need for large capital expenditures. Such a manufacturing process must further be capable of operating at the speed at which the fiber glass blanket is manufactured so as not to require slowing the rate of production of the fiber glass itself.